1. Field of the Invention
The present general inventive concept relates to a method of fabricating black matrices of a color filter, and more particularly, to a method of fabricating black matrices of a color filter to improve a brightness uniformity of light.
2. Description of the Related Art
Cathode ray tube (CRT) monitors have been widely used to display information processed in electronic media devices such as TVs or computers. Recently, as the requirements for large size screens have increased, flat display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting diodes (OLEDs), light emitting diodes (LEDs), and field emission displays (FEDs) have been introduced. Since a power consumption of the LCDs is small, the LCDs are commonly used for computer monitors and notebooks computer screens.
In general, the LCD includes a color filter through which white light modulated by a liquid crystal layer passes to form an image in desired colors. Conventionally, the color filter includes red (R), green (G), and blue (B) pixels arrayed in a predetermined structure on a transparent substrate. The R, G, and B pixels are partitioned by black matrices.
FIG. 1 illustrates a phenomenon in which inks filing the spaces partitioned by black matrices 11 of a conventional color filter mix with each other, and FIG. 2 illustrates a phenomenon in which light leaks due to inks insufficiently filling the spaces partitioned by the black matrices 11 of the conventional color filter.
Referring to FIG. 1, the black matrices 11 are formed by coating a transparent substrate 10 with a light-shielding layer, baking the light-shielding layer, and patterning the baked light-shielding layer into a predetermined shape to form the black matrices 11. The black matrices 11 partition a plurality of spaces on the transparent substrate 10.
When the black matrices 11 are weakly repulsive to ink and a contact angle is small, an ink 13 filling a space partitioned by the black matrices 111 to form a pixel overflows into an adjacent space to form an adjacent pixel and mixes with another ink 14.
To overcome this problem, a contact angle between the black matrices 11 and the ink 13 is increased by increasing a repulsive force therebetween. In FIG. 2, black matrices 21 that are strongly repulsive to ink 23 are illustrated.
Referring to FIG. 2, since the black matrices 21 are formed to have a strong repulsive force against ink 23 filling a space partitioned by the black matrices 21 to form a pixel is prevented from overflowing into an adjacent space to form an adjacent pixel and mixing with another ink 24. However, it is difficult to coat the inks 23 into the spaces partitioned by the black matrices on a surface of the transparent substrate 20 and obtain a uniform ink thickness.
Accordingly, light leaks from a side portion of the black matrices 21, and as a result, a brightness of light from each space partitioned by the black matrices 21 of the color filter becomes non-uniform.
To solve the aforementioned problem, conventional methods of flatly coating a transparent substrate with ink are illustrated in FIGS. 3 to 4B. FIG. 3 illustrates an “Ink-jet printing method and apparatus for manufacturing color filters” disclosed in United States Patent Publication No. 20030030715, and FIGS. 4A and 4B illustrate an “Ink-jet manufacturing process and device for color filters” disclosed in United States Patent Publication No. 20030108804.
Referring to FIG. 3, black matrices 31 are formed on a transparent substrate 30. A pixel space that is partitioned by the black matrices 31 is coated with an ink 32 to form a pixel, and air is blown over the ink 32 by using an air nozzle 33 to flatly coat the pixel with the ink 32.
Referring to FIGS. 4A and 4B, a pixel that is partitioned by printing frames 41 is formed on a transparent substrate 40. Shielding films 42 are formed on the printing frames 41, and electrodes 51 and 52 are respectively installed below and above the printing frame 41.
When an electric field is induced by applying a voltage supplied from a voltage source 50 to the electrodes 51 and 52 after the pixel is coated with an ink 60, a contact angle between the ink 60 and the printing frames 41 decreases to flatten a surface of the ink, as illustrated in FIG. 4B.
However, in the method illustrated in FIG. 3 of coating the pixel with ink by blowing air over the surface of ink by using the air nozzle, it is difficult to supply air to dry and flatten the surface of the inks in all the pixels before the inks dry. On the contrary, the flatness of the surface of the inks may deteriorate due to the characteristics of the inks.
Also, it is difficult to implement the method illustrated in FIGS. 4A and 4B of flatting the surface of the inks by applying the electric field to the pixels, since conductive inks are used in that method.